Why does my iPhone keep disconnecting from my home WiFi!

Okay, so I have an iPhone 5, and it's constantly automatically disconnecting itself from the Internet? I have tried everything to stop this. I've turned wifi on then off, aeroplane mode on then off, disconnected then reconnected, cleared cache and history of both safari and chrome, renewed the lease, turned my phone on and off, closed all recent program's, I've tried everything. It's not my wifi because I have it connected to my PC and it never disconnects itself, and its not the phone either because it happened in my previous phone (also an iPhone 5). Whenever the phone does disconnect itself, I just connect it again and it will cut out again after about 5-10 minutes! Why is it doing this!

It's not my Internet as I am currently using BT fibre optic broadband and the box is fairly new. I am also only a few metres away from the Internet HUB as its directly on the floor below me. I have just checked and I'm getting 36.5Mbps for my iPhone, so it definitely isn't the Internet.

Also, I have realised that it disconnects mostly when I'm watching any kinds of videos on my phone; such as YouTube, 4oD etc. It doesn't necessarily disconnect when simply browsing the Internet or playing an online game.

What can I do to stop it doing this!

Any help would be greatly appreciated because this is really starting to bug me now.

FDNi_x17.04.2013

There is either something in your house bumping the connection like a microwave or phone, or you are too close to the window and the phone is picking up the cell network data signal. Try going in the center part of your house and see if you get the same issues. If that doesn't work try deleting your router from the wifi menu on your phone and reconnect it like you did when you first got the phone.